Telephone-exchange system



A. E. UNDEL|.. TELEPHONE EXCHANGE SYSTEM. -v APPLlcATloN FILED Nov. 14,191e. 1,356,639.

A/ben f. Lu//me/ by A ,y.

A. E. LUNDELL. TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED Nov. I4, |916. 1

Patented Oct. 26, 1920.v

2 SHEETS-SHEET 2.

/MI/ena/f.- Alben L ande# n Nir E n r ALBEN E. LUNDELL, or' YoRir, N.Y., .assrGNoR To WESTERN ELECTRICv Y COMPANY, INCORPORATED, or NEYwYoRE,N. Y., A CORPORATION or NEW Y YORK. y

TELEPHONE-EXCHANGE sYsJTEM.

Appuauoii mea Novemberm, v'1916. serial No. 131,203.

T 0 @ZZV/whom t may concern Be it known that I, ALBEN E. LUNDELL, a

citizen of the United State s,'residing atNew Y change systems, andparticularly to means for applying ringing'current to .the called Yline. It has been found in practice that the number of inal switches isgreater than the number of certain v of the intermediate Y' switches,and therefore it has heretofore been proposed that the ringing equipmentbe placed at one lof such intermediate switches. In order to apply theringing current automatically at the proper` time, a steering switch hasbeen ,associated with such intermediate switch, which advanced one stepfor each switch usedpin the connecfY tion being built up,l and whenconnectionV was made with' the called line, radvanced to the ringingposition. Thus, ringing currentv wasV invariably applied Vwhenapredeter-` minednumber of switches had been set'. In` systems whichinclude private `branch exV change lines, however, the numbery ofswitches used in establishing a connection when a private branch.exchange line vis called is 4different from thatused in'an ordi-v naryconnection. The object vof the presentV invention is'to insurethe properoperation of the ringing equipment at the intermediate switch in` suchsystem, irrespective ofthe number of switches used.

Toattain this'obj ect there is provided, ,in accordance with thisinvention, .a-.controlling circuit successively established or main-Y Ktained in a given condition from the intermediate switch to and throughthe interven-A ino` switches to the final switch in the series by meansof which the ringing equipment is rendered effective upon thecompletion" of the connection to the wanted line. v

In the embodiment shown herein the invention isapplied to a machineswitching system,rand 'when the connection is extended to the switchsucceeding -that at which the ringing equipment is located, the con-`trol magnet of the steering switch is ener-V gized, such switch beingarranged to .ad-

vance upon the denergization of the Vcon- 'trol magnet( This magnet. ismaintained Specicaton of LettersPatcn-t. Ptlllietl 0015; 26, p i

energized 'in a circuit .at each succeeding1 ing switch vto theringingpcsition. vIf such line is busy,lmeans isautomatically` renderedoperative to prevent'such ringing current from being' applied tothei'called line,

and a busy tone is instead automatically applied tothe calling line;

.Referring to the draw1ngsFigures 1 and f 2 taken'toge'ther illustratediagrammatically one embodiment of the invention. 'In the embodimentshown, the line of the calling party A, upon initiating a call,may beconnected to an operators position in any well` knownnianner` VVhentheoperatorrlcarns' the number ofv the wanted line, she asso'-V ciatesherpsender113 by means of key K' with the leads 154and155 terminatingin` aiirst selector not shown.' Thisselector is then set by theoperatorl to pickout an idle incoming selector IS at the distantfofiice.

l The sender may be of the well-known finger wheel type which, uponrestoring','inter-VV rupts the line circuit a number of times co'r .n

responding to` the l'number ofthe digit of the called line involved.Whenfthe call has been extended to the incoming selector IS- atthedistance office, the stepping relay 100V thereaty becomes energizedover the followingv circuit: free pole of battery, contact 101 of. keyIf, conductor 155, arm 103 of the side switch of the` selector IS andits first con.y

ground. Relay 100 in attracting its arma-r` 110, and, .in attracting itsleft lV-armature, connects Vthe back contactof'relay 100 to the tact,stepping lrelay 100, arm 104, conduc- Ltor 154;, spring 107 and itslowercontact, contact 108 of the operators sender.v to

primary stepping magnet PM of the selecfV tor IS.

The operator now transmits the digit of.:` the wanted number with whichthe ,incom-f ing. selector IS is vconcernedby ymeans l,of

her sender 113, which interruptsfthe. circuit of relay 100 in thewell-known manner.

Upon each retraction of the armature'. of

Y' relay 100, an impulse is transmitted to mag-v trunks 130, 131,132terminating in connecnet PM, which steps the brushes 113', 114, torshaving access to the desired line. The 115 ofthe selector IS in aVprimary direc-k relayy 129 is slow-actingV and remains enertion intoOperative relationto the desired gized during the transmission of theimgroup of trunks. Relay 112 is included in pulses. In attracting itsarmature, Vit enseries with magnet PM, and being slow-actergizes theescape magnet 133 of the selecing, is maintained energized, notwithstandtor S, which is constructed toV release the ingthe interruptions in itscircuit, as the side switch upon its denergization in the armature ofrelay 100- vibrates. p This relay, well-known manner. c

in, attracting its armature, energizes the l/Vhen the sender 113restores and mainvside-switch escapement magnet 116 of setainsthecircuit of relay 100'closed, relay lector IS, which is constructed torelease the 129, afteran interval, retracts its armature,

2. In position *2, arm 117 connects the secl ondary.; magnet SM of theselector IS in normal'contact SONC side switch upon its denergization inthe thus denergizing magnet 133, which rewell-knownmanner. IVhen thesender v113 leases the side switch into position 2. In restores'and`maintains relay 100 energized, position'2 the interrupter 1341 isconnected Vslow relay`112, after a slight interval, betothe secondarymagnet SM over the side- Vcomes denerg'ized, and, in retracting itsswitch arm 135, and steps the brushes 136, armature, denergizes the`escape magnet 137, 138 over the selected trunk group. In 116 whichpasses the side switchvto position position 2 escapemagnet 133 is againenergized vover'larm 139 and secondary off- Busy trunks are circuit withthe interrupter V118, and arm those upon whose test multiples ground is119 energizes the escape magnet 116 over present. Consequently, theescape magnet the off-normal contact SON, which is 133 is maintainedenergized as long as busy opened upon the first secondary step of thetrunks are encountered. When the first unselector IS; Busy trunks arethose upon grounded test multiple 132 is reached, magwhose testmultiples 120 ground is present, net 133 is denergized and releases theside 5 asl will hereinafterV appear` the `escape magnet 116 ismaintained Yenerside-switch arm 123 of the selectorY S, in its gized aslong as busy trunks are encoun vsecond position,'maintains ground uponcontered.4 When the lirst ungrounded test mulductor 125 leading to theescapeY magnet tiple 120 is reached, escape magnet 116 becomesdenergized, passing the side switch intok position Arm 117, in lleavingposition 2, opens the circuit of magnet SM,-

'v thus stopping the selector with the brushes 113, 114 and 115 upon themultiples 121,

` 122 vand 120 .of the selected trunk. Inposi- 116 'of selector IS.Thisy arm 123 Vengages itssecond contact before it leaves its firstcontact, and engages its'third contact before leaving-,its secondcontact. Thus,as this arm reaches position 3, theA escape mag-Consequently, switch into position 3. It will be noted that net 116 isheld energized over the following circuit: free pole of battery, leftwindingV of tion 3, arm 119 grounds multiple 120, thus magnet 116,conductor 125, arm 124 and its causing the seized trunk to test busy tothird Contact, brush 114,'multiple 122, arm other selectors and`energizes release relay 123 and its third contact,`brush 137, mul-V'RRg which, inattracting its armature, intiple 131, side-switchV arm 200of connector Arm terposes a break in the circuit of release C- and vitsyfirst contact to ground. magnet RM of the selector S. In position,"139, in its third position, grounds theV mul- 1 of the selector S,side-switch arm 123 tiples 132 of the seized trunk to render the thereofcloses the following circuit for the same busy, andalso operates arelease relay escape magnet 116 of the selector IS: R2R2 oftheconnector, which, in attracting ground, arm 123 and its firstcontact, multiple 12,2, brush '1141, arm 124: and its third contact,conductor 125, magnet 116, free pole of battery. The escape magnet 116be-L comes energized when this circuit is closed, but does not releasethe side switch.V The operator4 now transmits the next digit'V of thewanted number. Upon each retraction ing circuit to primary magnet P2M2of the 120 of the armature of relaylOO, an impulse is transmitted overthe following circuit to the nal v121, arm 128, slow relay-129, magnetPVM, free V pole of battery. The selector S is jfthiisstepped in aprimary directionlin operative relation to the desired group of tainedenergized during the transmission of 131')` connector: armature and backContactY of the impulses, and, in attractingA its armature, Venergizesthe escape magnet 203 of the connector side switch which is constructedto release the side switch upon its denergization in the well-knownmanner. The

connector brushes 204, 205, 206 are thusA driven in a primary directioninto operative relation to the group of terminals containing those ofthe desired line 207, 208', 209. When the ,sender restores and maintainsrelay 100 energized, slow relay 203 after an interval, becomesdenergized, and,

in retracting its armature, denergizes the' escape magnet 203 whichpasses the side switch into position 2, in which position arm 201substitutes the secondary magnet SZMZ for the primary magnet AP2M2 yinthe stepping circuit. Arm 200 in position 2 maintains ground uponconductor 140 con-k nected to the escape magnet 116, thus hold-V ing thesame energized. p

The operator noviT transmits the units digit of the wanted number.retraction of the armature of relay 100 an impulse is transmitted overvthe circuit traced to the arm 201, from whence it passes over conductor210 and the left windingV becomes denergized, andin retracting itsarmature denergizes magnet .203, whichpasses the side switch intoposition 3, in which the test ofthe selected line takes place. Arm 200,in moving olf its second contact, removes ground from conductor 140,connected to the escape magnet 116,0f the selector IS. The escape magnetthereupon de'e'nergizes and passes the sideswitch into positionr4.Whenthe sender-113m stores, after transmitting the unitsimpulses,

the operator throws the key K, so that the springs 101, 107 engage withtheir upperv and lower contacts, respectively, thusdis-v connecting thesender, from the leads 154, 155 and connecting the battery 157 thereto.

`Arm 104, in position 4, closes the. following circuit for relay 141;free pole of battery,

relay 141, upper left-hand winding of re- I peating coil RC, arm 104 andits fourth contact, conductor 154, spring'107 and its upper contact toground. `Relay 141, in ate tractingits armature, energizes ringing relay142 over the following circuittground, armature and front contact ofrelay l141, conductors 143, 144, armature and back contact of ringingcut-olf relay RCO,arma ture and back contact of relay 145, con-V ductor146, relay 142,;free pole offbattery.

Upon each Relay V,142, in attracting its armatures, con-V nects thelfree pole of generator 147 tov the side-switch arm 200, and ground Ytothe arml 201 preparatory to projecting theringing, f

current over the selected line. In' parallel with therelay 142, a relay150 is energized, and in attracting its left armature, energizes relay110. Relay f 110, in attracting its left armatura-opens the lockingcircuit of-re'lay 109 and'interpos'es a break in the circuit of releasemagnet RM. Y

11s stated, in position 3 of the connector side switch, the calledlineis tested. If. the se`` lect'ed line is idle, full potentialis presentupon the test multipleV 209 thereof, and the test relay 211 becomesenergized over the following circuit: free pole of battery, cut-off.' .Yrelay CO, multiple 209, brush206, both windings of relay 211 in series,arm 215 and its third contact to ground. VThe test krelay 211, inattracting its right armature, shunts out its right-hand high-resistancewinding, thus so reducing the potential'upon ,the test multiples 2,09 ofthe selectedline that it will test busy to otherconnectors, In ,position3arm 216 closes a circuit to energize relay 212.l Relay 212, inattracting -its'rightarmature, closes the vfollowing circuit `for Aconvnectork escapev magnet 203" which isl constructed to release the sideswitch from 'position 3 to'position 4, 'uponfits energization ground,right armature and front conta'ctrof relay 212, left armature andfrontjcontact of relay 211, magnet 203 ,to free poleof bat-4 tery.lnvposition 4,'arms201 andf200 extend the ringingfcircuit to the calledline, where- Y upcn the bell 216thereat is rung. 'The-ring ing circuitis as followsrfree pole/:of ringing generator 147, relay RGO, lowerarmature.`

and frontcontact of relay 142, arm 124and its fourth contact, brush 114,multiple 122,

.arm 123 and its third contact, conductor 140, brush 137, multiple 131,arm 200 .and-its fourth Contact brush 205, multiple 208,`con f denser217 ,bell 216, multiple 207, brush204,

arm 201 and its fourth Contact, multiple 130, n

brush 136,1arm1281andfitsthird Contact,

multiple 121, brush 113,-: arm 127 and its'v' -fourth contact, upperarmature and frontl contact ofrelay 142 to ground; When the V*subscriberat.substation B removes lhis ree" 'ceiver'from the hook, thefr'elay.RCOgbe-,r comes energized, and, in'attracting its arniafv ture, removesthe shunt from about relay 145, which thereupon becomes energized inseries with relay 142, and in attracting its armature shunts out relay142 and locks itself up to ground at the armature and;V`V

front contact of relay 141. Relay 14,2, in i Y retracting its armatures,disconnects the ringing generator 147 'from thecalled line,"andf'connectsl thereto the a repeating coilfrr.- RC. Upon theretraction of the armatures of 5 relay 142,v talking V'current is,fedtothel I called lineover the following path :"vfree pole of battery,lower right-hand winding of repeating coil RC, called supervisory relay151, lower armature and back Vcontact of relay 142, arm 124 vand itsfourth contact,

Y brush' 114, multiple 122, arm 123 and its .third contact, conductor140,'brush 137,

multiple 131, arm 200 and its fourth contact, brush V205, multiple 208,through the Y telephonie apparatus at substation B, multiple 207, brush.204, arm 201 and its fourth contact, multiple 130, brush 136, arm 128and its third Contact, multiple 12,1,brush 113, arm 127 and its fourthcontact, upper armature and back Contact of relay 142, upper right-handwinding of repeating coil RC, to ground. Relay 151,-in attracting .itsarmature, closes the following circuit 'leading to the operatorsposition: ground,

right armature andV front contactrof relay 150, ,armature and frontYcontactY of relay 151, impedance coil v152, lower left winding ofrepeating coil RC, arm 103 and who thereupon operates the key K to breakA the Vcircuit of relay VY141. Relay 141, in retracting itsarmature,denergizes relay 150,

which,in retracting itsr left armature, de-

energizes relay 110 which closes the release circuitV of theselectorIS'as follows: release magnet RM, 'primary off-normal contact PON, rightarinature and back Contact of relay 109, left armature and baclrcontactof relay 110 to ground. The release magnet,

inenergizing, withdraws the pawls from the Vshaft of'se'lecto'r I-S, andalso restoresthe side switch in the welljlnown manner. The restorationof the selector IS denergizes relay RR ofthe selectory Sv, which, inretracting its armature, energizes the release magnet RM,of saidselector over the oifnormal contact PONY; 'Magnet RM, in

energizing, locks itself inV a circuit including such off-normalcontact, which' opens when.

the shaft of the selector reaches its normal I Y position, thusdenergizing such magnet.

Similarly,the restoration offselector `S deenergizes relay R2R2 fof theconnector C, which, kin'retracting its armature, energizes the releaseVmagnet R2M2 of the connector over the off-.normal contact P2O2N2. ThisVmagnet similarly locks itself over such off- Y normal contact andrestores the connector V'side switch-. When thel connector brushf'239interposes abreak in the circuit of reshaft reaches its normalposition'and opens 'i f the off-normal contact P2021 2, release magnetR2M2 is de'energized. Ifythe lselected operator to transmit'vthe tensdigit of the'Y line is busy, insufficient potential is present upon thetest multiple 209 thereof to energize `,the test relay 211.Consequently, this relay remains inert, andy at its back contactconnects the grounded pole of the battery to the ringing cut-off relayRGO over the rightarmature and front contact of relay 212, left armatureandbackcontact of relay 211, resistance 213, Aarm 200V and its thirdcontact, multiple 131, brush 137 ,f conductor 140, arm 123 and itsthirdcontact, multiple 122, brush 114, arm 124 and its fourth contact,lower armature and front contact of relay v142, relay IGQ, ringinggenerator 147 to` ground. The marginalv relay RC() becomes energizedwhen this circuit is closed, and in attracting its armature, removes theshunt from about relay-145, which thereupon energizes in series withrelay 142. In attractingits armature relay 145 shunts out relay 142 andlocks itself to groundl at the armature and. front'contact of relay 141as described'. Relay V142, in retracting its armatures, conn'ects therepeating Vcoil RC to conductors 148 Vand 149, whereupon the followingcircuit is closed from the source of busy tone current 214 to notify theoperator that the selected line isV busy: ground, secondary windingofthe source of busy tone current 214, condenser 215, left armature andAfront contact ofIr-elay 212, arm 201 and its third Contact, multiple130, brush 136, arm 123 and its third contact,;multiple 121, brush`113,1arm127 and its fourth contact, upper armature of relay 142 and itsback Contact, upper right winding of 'repeating coil 'BCto ground. Theoperator hears this tone by induction through the windings of repeatingcoil RC, and informs the calling party that the desired line' is busy,and releases the connection as described.

lAssuming now,v that the called line is located in a private branchexchange. In this casethe operation is the same as that described,yexcept that the selector IS, instead of selecting.. selector S, picksout another selector similar -to S, vwhich has access to the connectors'C' in the private branch eX- change.r Assuming, therefore, that aselector similar to S has been set on the multiples 213, 219 and 220 ofa connector in the private branch exchange, when the brush 137V thereofengages the multiple 219, the following circuit'is closed to maintainthe escape magnet 116 ofv incoming selector IS renergized: ground,armf237 and the first contact Y of the side switch offconnector C, relay239, multiplev 219, brush 137, arm 123 and its third contact,multiple122, brush 114, arm

124 and its third contact, conductor 125,-

magnet 116, free pole of battery. The relay lease Vrelay VR3R3 of theconnector.

The sender 113 is now actuated by the Y wanted line.

armature of relay 100 animpulse is transmitted over the followingcircuit to the primary stepping magnet PSMS of the' con nector C at suchprivate branchy exchange:

armature and back contact of relay 100,

Aarmature and. front contact of relay 109,

conductor 126, arm 127 and its third contact, brush 113, multiple 121arm128 and its third contact, brush 136, multiple 218, arm 221 of theconnector vside switch, conductor 222, right winding of slow relay 223,magnet PSMS, free pole of battery.` Relay 223 remains' energized duringthe transmission of the impulses and closes a circuit to energizeconnector sideswitch magnet 230. The ma'gnetvPlif3 thus stepsth'econnector brushes'224,`225 and 226. in oper-` ative relation to thegroup containing the desired line 227, 228 and 229. When the sender '113restores and maintains relay 100 energized, the slouT relay 223, afteraninterval, becomes denergized and opens the circuit of escape magnet 230,which releasesl battery. Relay 223, as before, remains ener-v gizedduring the transmission of the imulses and in attractin its*V armatureenergizes escape magnet 230. Y When they sender restores and maintainsrelayrlOO energized, slowrelay 223, after a slight interval, retractsits armature, denergizing magnet 230, which passes thesideswitchintoposi- Y tion 3. If the selected linel is idle,unshuntedpotential is present upon the'test multiples f229 thereof, and thefollowing circuit is closed: yfree pole of battery, cut-offrelay 232,multipley 229, brush 226, ywindings of .test relay 233, armv 234' andits thirdy contact to ground. Relay 233, 'in attracting its rightarmature, shunts out its highresistance winding which so reduces thepotential upon the multiples 229 of the selected'lin'e as to cause it totest busy to other connectors. In attracting its .left armatura-'thisrelay closes the following circuit to 'energize 'the' escapementmagnet-230 :free pole-of battery,

magnet 230, left armature andffront contact of relay 233, rightarmatureand front contact 'of relay 235, to'ground,Ak relay 235 being energizedover arm` 236 and its third` g contact at this time. The "escapev magnet230 is constructed to release the side switch into .position 4 uponitsenergization. As hereinbefore described, when the arni 237 Upon eachVretraction of the l Which corresponds to arm 200 y'of Vthe `c0,n nectorC passed off its secondcontact, the escape magnet 116 of the selector:IS be. comes denergized and releases theV vside switch of said'selector into its fourth position,`in which relay 142 becomes energized,

as'described, to connect ringing generator 147 to the called line Dtoring the bell238 over the followin circuit; free pole of generator147, yrelay CO, lower armature `and front contact of relay142, arm 124,brush 114, multiple 122, arm 123 and its thirdcon--tact,-conductor'140brush 137,.multiple'219,`

relay 239, arm 237` and its fourth contact, 1

brush 225, multiple 228, bell 238, and condenser 240 at stationi),multiple 227, brush 224, arm 221 and ,its fourth contact, mul

tiplef218, brush136,l arm 128 and itsthird contact, multiple 121,brush113-, arm-,3127 andV its fourth contact', `-upper armatureand frontcontact' of relay 142 to'ground. i Y f Upon the removal of thereceiverjatf substation D, ringing cut-oifjrelay'RCOis 'ener-V gized asdescribed, from which point .the op'- f erations are the sameasthosetraced. The function of relay'239 is to remove relay '.241

from the talkingcircuit.' Talkingcurrent is fedk to thev calledv stationat the private branch exchange lover the 'windings' ofref-VA peatingcoil RG, the calledsupervisoryre'- the conclusion of the `conversationand *the gized, the former operating theusual supervisory` lamp beforevthe operator andthe lat-f.

'95 lay-239 being included in this circuit. V'Upon replacement of the'receiver by the called j i party, relays 151 and 239 becomedener-- lter interposing a break in thej circuit of relay R31? topreventpremature release.' `The Voperator now, by means of theykeyfK,-re

stores the'selectorsV IS and S. f'vWhenvthe:

241 is interrupted, whereupon thefollowing circuitis closed-for therelease relay '-RSR? of the connector: free Apole of battery, ,relay i lRaRa, arm 240 and its `fourth contact, armature'and back contactfof:relayl 241,` left armature and back contact @of relay.1239, lground.'vRelayRRs, in attractin 'ritsVv arvmature, -energizesV release magnet;3M8 ofv vthe connector .over therofffno'rnialcontact lBSN whichthereupon energizesyand in attr-acting its armature, locks itself'overfsuch1 i off-'normal contact; .When theixconnector brush shaftrestores and opens.thiscontact,I` Y v 120.," If the.- selected linefha'dbeen busy, ithe I Y potential ypresent Tupon thev `multiple 229 thereoflwould have .been insuicient tof energize'test relay 233, as described. fThererelease magnet RSMS. :becomes denergiz'ed.

vlay 2,35, in thethir'd lor testing position, is]` however energizedover arm 236, .andi'main-V ytrains relay 239 `energized over thefollowing.

circuit to preventpremature release z ground,

right armature ofrelay; 235 yand, its front contact, .left armature'olelay 233i 11d? its 105 v vselector S is restored, the circuit ofIrelay' v leef Vir.125

.3o l Y- A relayR3R3-of the connector over the folrvlowing circuit:ground, lettarmature and front contact of relay 142, relay RGO, ring-Ving.generator14"/ to ground. Relay RC) operates as hereinbeforedescribed, resulty ing in the deenergization of relay 142, which 10,

connects the right half of the repeating coil to the conductors 148,149.The attraction of the left inner armature of relay 235 connectsa sourceof busy tone current 243 in circuit with the repeating coil R il', toindicate to the operator that-the desired line is busy. This circuit isas follows: ground, secondaryk winding-244, condenser 245, inner leftarmature otrelay 235, arm'221 andits Vthird contact, multiple 218, brush136, arm v.128 and its, third contact, multiple 121, brush 113, arm 127Vand its kfourth contact, upper i ..armature andv back contact-"of`relay 142,

' `repeating coil RC to groundl. The oper` l,ator will then inform. thecal-ling party-of Vvthe busy condition of the desiredfline, and flWillbreak downtlie connectionbyi actuat- *ing thel key K -and restoringthe vselectors -lSvvand S. The Yrestorationof lthese selec- Y.torsfde-nergizes relay 239which, in retracting itslleftarmature,energizes,y the release i -backcontact of relay 239, armature and back AY' contact. ot'relay 241,* outer lett armature of i f VRelay R3R3, inattracting its armature, op-

relay; 235, relay'RSRS, free pole ot'battery.

" crates. the release' magnet RQMSV as before described, and alsorestores the side switch.

From the foregoing it is evident that the circuitfarrangement of thisinvention is particula'rly advantageousA in machine switchingY'ltelephone Vexchange systems :employing priyate `branch exchangeYworking, Since the side jswitch ofthe incoming selector will re-V `mainin its third vposition .until the last setxofV impulses issent,irrespective of the number of sets of suchimvpu'lses, whereasv insystemsr ofthe prior art, wherein the ring- Ving"equipment was locatedat'the incoming selector, the ringing control switch advanced onestepfor each set of impulses and inva- V"riablyv applied ringing current atthe end of y' jlapredeterinined numberlofsaid sets of impulses. A

v p .o Y m V1. Iny 'aF-telephone exchange` system, the combination withtelephoney lines, vlink 'cir'-l Vc'uits terminating in automaticswitches, a

:rotary auxiliary switch associated with'each circuit, means fordeenergizingvsaid mag-kk the saine, meansztor interconnecting a net whenthe connector -is seton the called Y What' is claimed is:V Y

ofzsaid automatic switches lfor controlling ff ing and acalledyline overa number yof said flink circuits vand automatic switches in series, avsource of signalingcurrent at an intermediate oneof said link circuits,aneleczation, a closed circuit including said deviceV`A Vand the linkcircuits in series automatically established and maintained, andmeansior made with the called line device. Y 2. In a telephone exchangesystem, the

to operate said combination with telephone lines, switches yadapted tointerconnect the'saine, a'rotary opening said ,circuit when connectionis Y auxiliary switch associated with each otsaid i switches to controlthe same, a source of signaling current at an intermediate lone ont saidswitches, and an electromagnetic responsive .device for operatingitsVassociated auxiliary switch to connect said source to said intermediates'witcliupon its -deernergiclosed circuit extended to Aeach succeedingsaV ization, means for including said device ina switch in series, andmeans for openingV said n circuit when connection is made' with thecalled line to operate said device to connect saidV source thereto. Y YY c 3.1n a telephone exchange system, the

combination with telephone lines, link cir- Y cuits, means forinterconnecting A,a calling and a called lineovera number of said link;

circuits in series, a source ot signaling cur- Vrent at an intermediateone ofsaid link circuits, asteering switch at each or" saidlink circuitsto control the same,a magnetv associated with the steering switch' of.the in-f termediate link circuit adapted'to advance the same to connectsaid source to vsaid link circuitk upon vits denergization, means `forenergizing said magnet, means for main- 'taining saidv magnetenergizedfincludiiig a circuit at yeachsucceeding link circuit, andmeans for deenergizing said magnet when Y the connector is set on. thecalled'line.

4. In kav telephone yexchangesystem, the

combination with. teleplione'lines,` link cir` cuits terminating Vinselective switches, means for interconnecting a` calling and a calledline overy a number ofsaid link circuits in series,` a source ofsignaling current atan intermediate one of said linkfcircuits,` amulti-position steering switch lat eachk of' said link circuits vtocontrolthe same', a magiooV Y net associated with the steeringswit'chYot Vsaid intermediate link circuit adapted Vto advance the same toconnect said source to 1 saidulinkcircuit upon'its deenergization, vvvmeans for energizing said magnet;- means for maintaining saidl magnetenergized in- `cluding a'circuitpa't each succeeding link g .125`

line, and meansV for preventing said signalfisioV l.

1,356,639 Y l l2 5. In a telephone exchange system, the lcludingtheauxiliary switch at said inter combination with telephone lines,automatic mediate link circuit adapted to connect said switchesincluding selectors and a connector, source to the conductors Vof saidlink cir-v stepping magnets therefor, a sender adapted cuit, a magnetfor operating said switch 55 to operate said magnets to set suchswitches when denergized, a closedcircuit' therefor to interconnect saidlines, a source l'of sigincluding said link circuits in series, andnaling current at lan intermediate selector7 means for automaticallymaintaining said aside switch for each of said selectors to circuitclosed until connection is made with control the same, means foradvancing the the called line, and means automatically op- 60 1osteering switch of said intermediatey selecerated if the line is busyfor preventing the tors when said selector is set to place saidoperation of said magnet from becomingV sender in operative relation tothe magnets ecctive to applycurrent to the called'line. of thesucceeding switches, means for main- 8.' In a telephone exchange system,the.. taining said steering switch in said posicombination vwithtelephone lines, link cir- '65 tion while said succeeding switches arebecuits terminating in automatic switches, ing set7 and means foradvancing said steer-` means for interconnecting a calling and a ingswitch to connect ysaid source of signalcalled line over a number ofsaid linkl ciring current' to the selected line when the cuits landautomatic switches inseries, a connector is set thereon. y Y rotaryvauxiliary' switch associated with each 7.0 V 6. In a telephone exchangesystem, thev ofsaid automatic switches for controlling y combinationwith telephone lines, automatic 'the same, a source of signalinglcurrent at switches including selectors and a connecan intermediateoneof said ylink circuits, a tor.; st ping`magnets therefor, a'V senderdevice including' the auxiliary switch at ,/L/daptied to operatesaidnagncts to set such said intermediate link circuit ladapted to 175 cconnect said source to said linkcircuitnpon switches to interconnectlines a source p l y ts denerglzation, avclosed circuit Vinclud-fLN ofsignaling currentfat one of s lecto a side switch-for said selectorincludi'n escapement magnet adapted to ad side switch upon itsdenergizati' for' dener'gizing said magnet whe' lector'is seg-t toadvance saidA sil place saids'ender in operative relv 'f magnets of thesucceeding switch for again energizing said escape? 35 cluding a circuitat the succeed and for maintaining the same enterb cluding a circuit ateach succeedinv si i-tcl closed before the corresponding the precedingswitch is opened '40 for denergizingsaid escape magnet .to ac 4 vancesaid side switch to connectlfsaid source of signaling current to thevselected lin when the connector is set thereon.` v 7. In atelephoneexchangegsystem, th combination with teephone lineslink .circuits including switches, a rotary auxiliar' switch at each of said`-switches'gjfineansifor interconnecting a calling and '-gfcalled lin overa number of sai'd link'circuitsinserie ng said device and the linkcircuits iny series i automatically established/and maintained, p "i-means automatically actuatedwhen" connection' is made with the calledline for endering said circuit effective to operate aiddevice. l f

9. In a telephone exchange system,tele )hone lines, link circuitsterminating in iutomatic switches, each of saidL automatic 'witchesbeing provided with a step by step uXiliaryv switch for controlling thesame, means including said link circuits and auto!r natio switches inseries for interconnecting calling and a called line, a source of ringngcurrent at an intermediate switch of the series, and means located atsaid interme- :diate switch andv controlled successively over said flinkcircuits for connectingsaidt .source of ringing current to the series ofink circuitswhen'the called line is.. found. f Inrwitness whereof, Ihereunto subscribe Q y name this 13th day of November,` A. D. 916'.V Y 1

